A conventional skateboard is set in motion by its user standing on the skateboard with one foot and pushing off from the ground with the other foot. In the process, it is of disadvantage that additional acceleration can only be achieved by continually pushing off from the ground, and thus the user can never maintain his ideal posture on the board for prolonged periods. Also, only limited speeds can be reached with the conventional skateboards operated in the manner described above, which represents a further disadvantage for the modern skateboard riding technique.
German Offenlegungsschrift No. 3,427,834 shows a skateboard on which two drive wheels arranged on the same shaft can be driven by a rocking motion of a pivotably mounted board. The rocking motion is transmitted to the two drive wheels by means of a chain which is guided over gears which in turn mesh with a pinion gear attached to the drive shaft.
In view of this type of drive, the board on which the user stands must be located exceptionally high, resulting in an unsafe standing position, which, moreover, makes riding around curves and also figure riding considerably more difficult. In the freewheeling position, in which the skateboard is supposed to roll along freely after the preceding drive, the user stands in either an uncomfortable sloping position or in the horizontal position at an increased height, which is unreasonable for normal skateboarding operation. Furthermore, with the drive wheels protruding laterally beyond the board, there is the risk of getting caught or tripping. For all these reasons the known skateboard is hardly likely to be suitable for practical use.
The drive mechanisms known from roller skis or roller skates cannot be adapted for use with skateboards since the rider would have to stand successfully with both feet on the same end. A rider would have to maintain his balance even when riding around curves. This does not permit these abovementioned mechanisms to be transferred to the skateboard construction.
A particular difficulty of designing a skateboard drive mechanism results from the board, elastically mounted on the wheel axles, being subjected to considerable tilting on curves. The drive connection mechanism disengages on curves.
It is the object of the present invention to propose a mechanically operable skateboard which corresponds to the normal overall height of conventional skateboards and, thus retains the diverse possibilities which the conventional skateboard offers the experienced user.
It is a further object of the present invention to provide a self-propelled skateboard having a drive mechanism elastically mounted to a frame which is allowed to tilt with respect to the frame.